In the Chinese industrial city of Yiwu, it's Christmas year-round. But entrepreneur Kevin Luo isn't in a festive mood. Roughly half the world's Christmas decorations  from plastic trees to red Santa caps  are produced by some 500 manufacturers in Yiwu. At a noisy facility outside the city center, Luo, 28, churns out 130 million shiny ornaments a year. A changing Chinese economy, however, is making it more and more difficult for his firm, the Yiwu Shuangyuan Christmas Arts & Crafts Factory, to stay...